Detection of sirens is discussed by a number of works.
U.S. Pat. No. 5,710,555 describes: “A siren detection system [controlling] the lights at an intersection to direct traffic [to] permit an emergency vehicle to travel through the intersection unimpeded. The system determines the frequency of the sound emanating from a siren carried by the emergency vehicle by counting pulses that indicate the frequency of the sound, by determining the elapsed time necessary to count a selected number of pulses, and by utilizing the elapsed time and number of pulses counted to determine the frequency of sound emitted by the siren.”
A similar idea is presented in U.S. Pat. No. 6,980,125:
“A warning light system for a traffic intersection for alerting pedestrians and operators of passenger vehicles to the approach of an emergency vehicle. The warning light system is activated only by sounds in the range of frequencies which are emitted by the siren of an emergency vehicle. The warning light system has a warning light assembly having a control unit, and also has an audio sensor unit. The warning light assembly has a blue light and a white light, which flash alternately and repeatedly, after receipt of an audio signal by the audio sensor unit from the siren of an emergency vehicle, and processing of that signal by the control unit. The lights of the warning light assembly continuously flash until the sound emitted from the siren is no longer detectable by the audio sensor.”
US patent application US 2005/0074131 A1 describes: “A sound processing system for use in an automotive vehicle of the type which includes at least one door and at least one door-lock comprises at least one sound sensor coupled to the vehicle for receiving a sound external to the vehicle, an alert generator for notifying an occupant of the vehicle when the external sound is an emergency signal, and a door control module coupled to at least one door-lock for unlocking at least one door.”
The above art (except US 2005/0074131 A1) does not suggest how to alert a driver of a vehicle of the presence of an approaching siren (e.g. from an emergency vehicle); or how to alert a driver of a vehicle of the presence of a different sound generated in the vicinity of the car, such as a car horn, or any sound which could be classified with more general parameters, such as a sudden onset sound (or “acute sound”).
This problem is particularly pertinent when drivers are listening to loud music or communications systems such as CB radios, or when operating their vehicle's ventilation system at high fan speeds, any of which may mask any warning sounds in the ambient environment.
US patent application US 2005/0074131 does not teach a method to determine the sound level within a vehicle, nor determine the degree of acoustic isolation of the internal vehicle cabin. The present invention adds this functionality so that the driver alert can be modified to maximize detection and intelligibility of the warning alert. Furthermore, the present invention enables the location of an external sound source (e.g. siren) to be determined by detecting the strength of the detected sound in different ambient sound microphones around the vehicle.